Rheostat



Oct. 8, 1929.

H. H. FROST RHEOSTAT Filed Deo. 5, 1924 2 Sheets-Sheet l Oct. 8, 1929. H H, FROST 1,730,499

RHEOSTAT 2 Sheets-Sheet 2 Filed Dec. 5, 1924 JQWWM @y di@ Patented' oct. s, 1929 UNITEDv STATES PATENT AOFFICE HERBERT H. FROST, OF CHICAGO, ILLINOIS, ASSIGNOR, BY MESNE ASSIGNMENTS, TO CHICAGO TELEPHONE SUPPLY COMPANY, OF ELKHART, INDIANA, A CORPORATION or DELAWARE nnnosrn'r Application filed December 5, 19,24. `Serial No. 754,023.

My invention relates to rheostats for light current work. In the control of current flow through the filament of an electron tube, or the like, it is desirable to have fine graduations for evenness of control. It is also desirable to have constant contact on thevmoving parts so that the resistance will not be varied by movement of the parts outside of the actual resistant conductor. It is also desirable, when there are relatively coarse graduations between successive contacts, to provide an intermediate variable or vernier so that even with relatively coarse graduations of the successive steps, a uniform control may be secured.

The rheostat of my invention is designed to secure the above desirable features in a simple and inexpensive manner.

Primarily I provide an improved base for mounting the co-acting parts which permits the making up of different forms of rheostats or controlling devices of diiferent character and capacity with a few standard parts and a minimum of labor. I employ this novel base member in making up, for example, a six ohm rheostat with Vernier adjustments, a thirty ohm rheostat without Vernier adj ustments, a potentiometer, and a control unit combining both aforesaid rheostats.

Next, I provide an improved vernier resistance device to fill in the variations between the successive stepsof the contact making member. This device includes a novel contact inger and novel means for moving the same.

I also provide an improved lead in connection for making contact with the moving arm or contactor. v

Finally, I make all the parts such that they may be assembled into a complete control unit embodying both the novel vernier and its parts with the novel lead in and its co-operating parts.

Now, in order to acquaint those skilled in the art with the manner of constructing and operating a device embodying, my invention, I shall describe in connection with the accompanying drawings, two specific forms of rheostats which I have constructed and which embodyl the invention.

In the drawings: Figure l is a front elevational view; and Fig 1A is a line diagram of the rheostat circuit.

Fig. 2 is a rear elevational view of a six ohm rheostat employing a Vernier adjustment;

Fig. 3 is a side elevational view of the same;

Fig. 4 is a section taken on line 4 4 showing the device mounted upon a panel;

Fig. 5 is a fragmentary section through the contact arm and Vernier;

Fig. 6 is a front elevation; and

Fig. 7 is a rear elevation of a thirty ohm rheostatl embodying my invention;

Fig. 8 is a side elevational view of the same;

Fig. 9 is a cross section taken on the line 9-9 of Fig. 6; and Fig. 10 is a fragmentary sectional View taken on the line 10-10 of Fig. 7

In the forms of rheostats which I have indicated herein, I employ a common base or body member l, which comprises a central disc 2 and an outer cylindrical rim or flange 3. Between these parts I provide an annular cylindrical slot 4 which may be employed as a suitable receptacle for the rheostat strip 5, having the resistance conductors 6 wound thereupon.

This rheostat strip comprises a thin flexible piece of ibre, or the like, upon which is lwound the resistance conductor 6, the resulting strip being suiiiciently flexible to be bent into circular form and disposed in the recess 4.

At the central part of the disc 2 I provide a molded sleeve 7 of metal, which sleeve has a head 8 upon the back side of the disc. The cylindrical surface of the sleeve adjacent the head is suitably knurled or otherwise formed to engage solidly with the molded material of which the body 1 is formed. This sleeve 7 is internally threaded as indicated at 9 to receive the thimble 10, which has external threads co-operating with the threads 9 and which has a suitable head-1l for engaging upon the outside of the panel l2, or other suitable mounting board.

The thimble 10 is a standard ack thimble such as is employed in the manufacture of telephone jacks. This thimble draws the panel 12 tight against the edge of the rim 3 so as to mount the body of the rheostat in position upon the panel. An integral pin 13 lis formed upon the edge of the flange 3 and this pin enters recess in the panel 12, so that when the thimble 10 draws up the panel against the edge of the rim or flange 3, the body of the rheostat will beheld against turning. The 1 is molded with a pair of slots 14 and 15 upon the edge of the flange which engages the panel 12. In the form shown in Fig. 1, these slots are not usefully employed, but in the form shown in Fig. 6, they serve as seats for terminals, as will be apparent later. The body of the rheostat has a solid portion at 16 where the slot 4. ends and, upon the front side of the flange 3, the flange 3 is recessed radially as indicated at 17 at a position corresponding to the lug 16. A radial hole 18 is formed in register with the recess 17, so that a terminal screw may be inserted therethrough for holding the central contact, which will be described in connection with Figs. 6 to 10, inclusive.

Between said radial recess 17 and the slots 14 and 15, I provide the steps 18 and 19 to provide seats for the heads of the bolts 20 and 21, which bolts have .the lock nuts 22 and 23 and the knurled thumb nuts 24 and 25. Now the purpose of this arrangement of slots, steps and recess brings the heads of the various terminal screws into different radial positions, so that suitable terminals and their bolts may be spaced at proper intervals about the outer cylindrical surface of the flange 3, without having the heads or'. inner ends contacting with each other, even though they are so close that they would otherwise engage. In the rheostat shown in Figs. 1 to 5, the rheostat strip 5 is set into the recess 4 and the ends of the resistance conductor 6 are led at one end, namely, as indicated at 27, to the terminal 24. The opposite end of the conductor 16 is unwound from the strip to leave the same bare for a distance, as is indicated at 28, this distance being great enough to permit the rheostat contact arm 29 to move back and forth from its limit position sufficiently to be moved bythe Vernier arm 30. The opposite end of the conductor 16 is terminated on the strip 5 at 31, as indicated in Fig. 2.

The cylindrical flange 3 has an outwardly extending im or circular shoulder 32 which is grooved peripherally to receive the Vernier resistance conductor 33, one end of which conductor 33 is fastened by passing the' same through the flange 3, as indicated at 34, and turning the end over on vthe inside. The opposite ends of the Vernier resistance conductor 33 is passed through an opening extending radially through the rim or flange 3, as indicated at 35, the conductor then extending di.

' agonally, as indicated at 36 in Fig. 2, to an The rheostat arm 29 is secured as by rivet-i ing over a flange 35 to a collar` 36 which collar is guided upon the reduced portion 37 of the operating shaft 38. At its opposite end the collar 36 has a slottedspring washer of generally conical'form riveted thereto, this conical spring washer 39 bearing against the head 8 of the sleeve 7. The mode of attaching the collar 36 to the spring washer 39 and to the hub of the rheostat arm 29 comprises the formation of a small extending neck or riveting flange, which receives the hub of the washer 39 and of the arm 29, and in each case is spun or riveted over so as to grip theinner periphery of the opening through which it projects. In like manner, the outer end of the shaft 38 has a reduced neck which is spun over the aperture in the hub of the Vernier arm 30 for rigidly securing t-hese parts together. The central or shaft portion of the Vernier arm 30 has a longitudinal corrugation formed therein for stiening the same. Now it will be seen that the Vernier arm is directly fastened to the shaft 38, whereas the rheostat arm is fastened to the collar 36. These two parts are, therefore, loose with respect to each other. However, the rheostat arm 29, which is normally loose from the shaft 37, has extending wings 40, the outer ends of which are bent up as indicated at 41 for engaging the sides of the arm 30, so that movement of the Vernier arm 30 from one wing to the other may be accomplished without moving the rheostat arm 29.

The outer end of the Vernier arm 30 is bent over the annular circumferential flange 32. This bent over portion 42 has laterally extending spring fingers 43 which are adapted to bear against the Vernier resistance conductor 33 with a balanced pressure, so that the arm 30 is less apt to be distorted or to run olf of the Vernier conductor 33. The bent over portion 42 has a finger 44 hooked back of the annular rim 32 in order to guide the contact fingers 43 along the resistance conductor 33.

An integral stop member 45 formed as an extension of the rim 3, serves to limit the motion of the arm 30. This stop is so placed with respect to the Vernier resistance wire 33 that the contact fingers 43 leave the Vernier 4resistance when the arm engages the stop.

- of the same.

is disengaged by the arm 29 when the arm 30 engages the stop 45.

In Fig. 1^ I have indicated the circuit diagram of the device shown in Figs. 1 to 5. It will be seen that the resistance conductor 6, which is wound upon the strip 5, is fastened at one end to the screw 20 and binding post 24 and it is adapted to be engaged by the contacting arm 29 which contacting arm 29 is moved by the vernier arm 30, this Vernier arm 30 being fast upon the shaft 38. When the parts are in zero position, as indicated in the diagram of Fig.`1^, the vernier arm 30 has its contacting fingers 43 off of the vernier resistance conductor 33 and the contacting arm 29 is off of the rheostat resistance conductor 6.

The shaft 38 extends out through the thimble 10 and is held in the knob 46, said knob having a metallic sleeve 47 molded in the body This sleeve 47 has a set screw 48 which lies in the recess in the molded material of which the knob 46 is composed. The inlaid sleeve 47 is closed at its inner end and at its outer end has a reduced collar which is adapted to be riveted over the hub of the pointer 50, this pointer indicating the position of the Vernier arm. The hub 49 of the pointer 50 lies flush with the surface of the knob 46 and is held by the grip of the riveted over collar.

The device is applied to the panel 12 as follows: First, the knob 46 is removed from the end of the shaft 38 by loosening the set screw 48, then the thimble 10 is unscrewed from the sleeve 7. lThe shaft '38 is projected through a hole in the panel 12, which. hole is la-rgc enough to receive the thimble 10. At the same time, the projection or stud 13 is set into a recess in the panel 12 to prevent the body of the device from turning. Then the thimble 10 is fastened in place and drawn up with the head 11 against the outer surface of the panel 12 to hold the body 1 in place upon the panel. Thereafter, the knob 46 is placed upon the shaft and the set screw 48 is fastened in place with the pointer 50 in line with the Vernier arm 30.

In operation, the knob 46 is t-urned, thereby moving the Vernier arm until it engages one of the stops 41 moving the rheostat arm 29 wit-h it until the same engages the resistance conductor 6. The device is so designed that the movement of the Vernier arm 30 over the portion of the Vernier conductor 33 between the lugs 41 on the rheostat arm 29 is of the same order of magnitude as the difference between successive contacts or windings of the resistance conductor'6. Therefore, the Vernierv fills in the gap in resistance occasioned by the difference between turns of the resistance conductor 6.

Inthe form shown in Figs. 6 to 10, the same bod 1 is employed and the same operating kno 46 is also employed for operating the device. In this case, a suitable resistance or rheostat strip 52 is wound with a relatively high resistance conductor 53, the turns of which are closely disposed with respect to each other upon said strip. The strip 52 is preferably made of flexible fibre, or the like, one end of the strip being clamped under a stop member 54 by means of the bolt 55 which lies in the slot 15. The resistance conductor 53 is removed from the strip 52 for a short distance adjacent the stop 54, so that the Contact arm 56 may ride off of the conductor 53 to open the circuit when the contact yfinger 56 engages the stop 54. This stop 54 is a small angular stamping of sheet metal. The bolt 55 has a nut 57 lying on the inner cylindrical part of the rim 3. The opposite end of the strip 52 is likewise clamped under an angular stop member 58, which is held by a bolt 59 lying in the slot 14. This bolt has its head lying on the inside of the flange 3, and a lock nut 60 holds the stop and contact member 58 in place upon the strip and in contact with the rheostat resistance conductor. A thumb nut or terminal nut 61 is fastened on the end of the screw and provides a readily released connector. The knob 46, which has a pointer 50, is identical with the similar parts shown in Figs. 1 to 5. The central sleeve 7, which is molded in the central disc 2, is identical with the similar parts as heretofore explained in connection with Figs. 1 to 5. Likewise the thimble 10 is the same as described in the previous form and it clamps the body 1 upon the panel 12 in the same manner, the stud 13 projecting in a recess in the panel in order to hold the body against rotary movement. The shaft 62, which projects into the metallic insert 47 in the knob 46, and which is held by the set screw 48, has a shoulder 63 which engages the reduced portion of the sleeve 7 at the head 8 to limit the inward movement of said shaft 62. A loose collar 64 is mounted upon the reduced portion 65 of the shaft 62 and a conical spring washer 66 is secured to the inner end of said collar 64 by means of a reduced neck which is riveted over the edge of said spring washer 66. This spring washer 66 need notI be riveted to the collar 64 but may simply underlie the same,

' if so desired. At its extreme outer end, the

shaft 66 is reduced in diameter to form the threaded extension 67, said threaded portion receiving the nut 68 to clamp the contacting spring 69 between the insulating'washer 70. This contact arm extends laterally over the fiange 3, as indicated at 71, and has its contacting finger 56 to which reference has already been made, engaging the conductor 53 on the strip 52 along the central part of the same.

This contact arm 69 has a central perforated hub which lies between the washer 70 and `which is insulated from the stud or reduced portion 67 by an insulating y,sleeve 72. The

contact arm l69 has a rearwardly extending port-ion 73 which is bent back to form a contact axially in line With the shaft 62. This contact 74 has a depressed portion which is adapted to receive the oint 75 of the contacting spring 76. This contacting spring 76 has a clamping foot 77 fitting the cylindrical surface of the flange 3 and being held by a bolt 78 and lock nut 79. The bolt 78 passes through the radial opening 18 heretofore referred to, and the head of said -boltlies in the recess 17, to which reference has also heretofore been made. The screw 78 has a. thumb nut 80 forming a suitable terminal.I It will .now be seen that one terminal of the circuit 80 connects through the spring 76 and contact point 75 with the tail or curved portion 7.3 of the contact arm 69, which through the finger 56, engages a resistance conductor 53, this resistance conductor 53 being connected at its ends to the terminal 61.

The depression 74 in the tail of the contacting arm 69 is provided to hold the point 75 in Contact With t-he same, even in case of slight inaccuracies in assembly. It is intend-` ed that the saddle or foot 77 shall fit closely upon the cylindrical flange 3 and be held by the bolt and lock nut 78, 79, so that said contact point 75 lies axially in alignment with the shaft 62. The spring 76 and the tail 73 of the arm 69 may be joined by an axially disposed bolt. The holes 2O and 2l, which were formed in the body 1 for the rheostat shown in Figs. 1 to 5, are not drilled in this case since they are not necessary. The contact arms, and springs, and the pointer of both forms of the device are preferably made of German silver. The method of mounting the form shown in Figs. 6 to 10, upon the panel 12, is the same in this form as that described in connection with the device shovvn v ig Figs. 1 to 5.

I do not intend to be limited to the details shown and described except as the same appear in the appended claims.

I claim:

1. In a rheostat adapted for mounting on l supporting panels of different thicknesses, a

base portion comprising a central disc having a peripheral upstanding flange, a tubular sleeve molded axially of said disc, a threaded clamping thimble cooperating with said sleeve to mount said rheostat on panelsof different therein of a diameter adapted .to receive said thimble, the thimble telescoping into said sleeve a variable amount depending upon the thickness of the mounting panel, the

thimble cooperating with said sleeve for l forcing said peripheral upstanding flange into abutting relation to the panel used, a shaft extending through said sleeve and thimble, a contact making member connected to vone end of said shaft, and an/ operating knob adapted to be moved along the other nesses, said panels having openings therein of a diameter adapted to receive saidthimble, thejthimble telescoping into said sleeve a Variable amount depending upon the thickness of the mounting panel, said central disc being v provided With an upstanding flange forspacing said base on said panel, a shaft extending through said sleeve on the thimble, a contact making member oppositely connected to one end of said shaft, and a knob adapted to be moved along the other end of said shaft into abutting relation with said thimble.

3. In combination, a panel, arheostat comprising a base having a peripheral flange contacting one face of the panel, a sleeve secured to the base, a thimble extending through the panel and having a flange contact'ng the other face thereof, said thimble telescoping the sleeve and having threaded engagement therewith, the thimble and sleeve cooperating with each other and with the flange of the base for clamping said base'to the panel, and an operating shaft extending. through the thimble and the sleeve.

In Witness whereof, I hereunto subscribe my name this 2nd day of December, 1924.

HERBERT. H. FROST. 

